Пусть x^2 - 4x+1 = t
t (t + 1) = 12
t^2 + t - 12 = 0
D = 1 + 48 = 49
t1 =( - 1 + 7)/2 = 6/2 = 3;
t2 = ( - 1 - 7)/2 = - 8/2 = - 4;
1) x^2 - 4x + 1 = 3
x^2 - 4x + 1 - 3 = 0
x^2 - 4x - 2 = 0
D = 16 + 8 = 24
√D = 2√6
x1 = ( 4 + 2√6)/2 = 2 + √6;
x2 = ( 4 - 2√6)/2 = 2 - √6;
2) x^2 - 4x + 1 = - 4
x^2 - 4x + 5 = 0
D = 16 - 20 = - 4
нет решений